scholarly journals Applicability Of Modified Ritchie-Knott-Rice Failure Criterion To Predict The Onset Of Cleavage Fracture For The Test Specimen With Residual Stress Introduced To The Crack Tip

2016 ◽  
Vol 2 ◽  
pp. 728-735
Author(s):  
Kenichi Ishihara ◽  
Takeshi Hamada ◽  
Naohiro Kikuya ◽  
Toshiyuki Meshii
Keyword(s):  
Residual Stress ◽  
Cleavage Fracture ◽  
Failure Criterion ◽  
Test Specimen ◽  
Crack Tip

J’s Disability Could Explain all the Test Specimen Size Effects Observed for the Fracture Toughness (Jc) of a Material in the DBTT Region

2015 ◽  
Author(s):  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Size Effect ◽  
Failure Criterion ◽  
Test Specimen ◽  
Crack Tip ◽  
Specimen Size ◽  
Finite Size Effect ◽  
Specimen Thickness ◽  
Deterministic Approach ◽  
Specimen Type

This paper summarized our recent studies on the test specimen size (TSS) effects on Jc of a material in the ductile-to-brittle transition temperature (DBTT) region. The validity of the deterministic approach to transfer the fracture toughness Jc obtained with different thickness specimens is demonstrated in these works. Based on the detailed finite element analysis results, it was found that the crack-tip stresses were different at the identical J in the test specimen thickness (TST) effect on Jc observed with both the non-proportional and proportional specimens. And adjusting loads to make the stress level equivalent showed increment in J that was equivalent to the Jc difference due to TST effect on Jc. This was similar with the past result obtained for the planar size effect on Jc (the difference in Jc due to the planar specimen configuration including crack length difference for the same specimen type or the specimen type difference). Thus, it was concluded that all of the TSS effects on Jc could be explained as due to J’s disability to characterize the crack-tip stress field accurately, or in a more general explanation, due to the finite size effect. In addition, the (4δt, σ22c) failure criterion (Dodds et al., 1991) was verified to transfer Jcs obtained for different specimen thicknesses and planar configurations. The critical value σ22c varied for only a few percent. The fact that these critical values were always reached at the specimen mid-plane and the fact that cleavage always initiated at the specimen mid-plane supported the validity of the deterministic approach. Because the (4δt, σ22c) failure criterion requires only “single” set of test data for Jc transfer and because σ22c shows only a few percent scatter, it seems to have a possibility to replace what Weibull stress is expected to do.

scholarly journals Predicting How Crack Tip Residual Stresses Influence Brittle Fracture

2002 ◽  
Author(s):  
Saeid Hadidimoud ◽  
Ali Mirzaee-Sisan ◽  
Chris E. Truman ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Experimental Studies ◽  
Crack Tip ◽  
Distribution Model ◽  
Relative Importance ◽  
Local Approach ◽  
Weibull Parameters ◽  
Experimental Scatter ◽  
Crack Tip Blunting

A probability distribution model, based on the local approach to fracture, has been developed and used for estimating cleavage fracture following prior loading (or warm pre-stressing) in two ferritic steels. Although there are many experimental studies it is not clear from these studies whether the generation of local residual stress and/or crack tip blunting as a result of prior loading contribute to the enhancement in toughness. We first identify the Weibull parameters required to match the experimental scatter in lower shelf toughness of the candidate steels. Second we use these parameters in finite element simulations of prior loading on the upper shelf followed by unloading and cooling to lower shelf temperatures to determine the probability of failure. The predictions are consistent with experimental scatter in toughness following WPS and provide a means of determining the relative importance of the crack tip residual stresses and crack tip blunting. We demonstrate that for our steels the crack tip residual stress is the pivotal feature in improving the fracture toughness following WPS. The paper finally discusses these results in the context of the non-uniqueness and the sensitivity of the Weibull parameters.

scholarly journals Applicability of the Modified Ritchie-Knott-Rice Failure Criterion to Examine the Feasibility of Miniaturized Charpy Type SE(B) Specimens

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Toshiyuki Meshii ◽  
Teruhiro Yamaguchi ◽  
Yuma Higashino
Keyword(s):  
Cleavage Fracture ◽  
Failure Criterion ◽  
Critical Stress ◽  
Small Difference ◽  
Crack Opening ◽  
Width Ratio ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Opening Stress ◽  
Crack Tip Opening

This paper examined whether the modified Ritchie-Knott-Rice (RKR) failure criterion can be applied to examine the feasibility of miniaturized Charpy type SE(B) specimens of thickness-to-width ratio B/W=1. The modified RKR failure criterion considered in this paper is the (4δt,σ22c) criterion which predicts the onset of cleavage fracture when the midplane crack-opening stress measured at a distance equal to four times the crack-tip opening displacement, denoted as σ22d, exceeds a critical stress σ22c. Specimens with B values of 25, 10, 3, and 2 mm (denoted as 25t, 10t, 3t, and 2t specimens, resp.) manufactured with 0.55% carbon steel were tested at 20°C. The results showed that the modified RKR criterion could appropriately predict the occurrence of cleavage fracture accompanied by negligibly small stable crack extension (denoted as KJc fracture) naturally for the 25t and 10t specimens. The modified RKR criterion could also predict that KJc fracture does not occur for the 2t specimen. The σ22c obtained from specimens for the 25t and 10t specimens exhibited only a small difference, indicating that the Jc obtained from the 10t specimens can be used to predict the Jc that will be obtained with the 25t specimens.

Deep Hole Drill Residual Stress Measurement Technique Experimental Validation

2006 ◽  
Vol 524-525 ◽  
pp. 549-554 ◽  
Author(s):  
W.R. Mabe ◽  
W.J. Koller ◽  
A.M. Holloway ◽  
P.R. Stukenborg
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Test Specimen ◽  
Experimental Validation ◽  
Stress Measurement ◽  
Reference Solution ◽  
Deep Hole ◽  
Element Analysis ◽  
Validation Test

This paper presents the results of an experimental validation of the deep hole drill residual stress measurement method. A validation test specimen was fabricated and plastically loaded to impose a permanent residual stress field within the specimen. The validation test specimen was designed to provide a variety of stress profiles as a function of location within the specimen. A finite element analysis of the validation test specimen was performed in order to provide a reference solution for comparison to the deep hole drill experimental results. Results from experimental testing of the validation test specimen agree well with the finite element analysis reference solution, thereby providing further validation of the deep hole drill method to measure residual stresses.

Accounting for Constraint in Probabilistic Fracture Mechanics Analysis of Welds in Floating Production, Storage and Off-Loading (FPSO) Vessels

2003 ◽  
Author(s):  
Jens P. Tronskar
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
North Sea ◽  
Failure Probability ◽  
Crack Tip ◽  
Probabilistic Fracture Mechanics ◽  
Crack Tip Constraint

Revision 4 of the British Energy R6 document: “Assessment of the integrity of structures containing defects” provides methods to allow for loss of crack tip constraint for shallow weld flaws. The document also provides methods to estimate upper-bound values of the through thickness residual stress distribution for a range of common weld joint configurations. The present paper presents results of analyses where approaches to modify the R6 Option 1 or 2 failure assessment diagrams (FADs) for loss of crack tip constraint pertaining to primary and non-uniform residual stress have been applied. The modified FAD were formulated for probabilistic fracture mechanics analyses of semi-elliptical surface cracks located at transverse deck welds of Floating Production, Storage and Off-loading (FPSO) vessels designed to operate in the North Sea. The objective was to study the influence on the failure probability of modifying the FAD for constraint and allowing for non-uniform residual stress. Another objective was to study the influence of constraint correction on the combined fatigue and fracture failure probability for the vessels subjected to wave loading. Material and weld tensile properties and fracture toughness distributions for input to the probabilistic fracture mechanics analyses were obtained from testing of welded panels prepared using welding procedures for actual FPSO fabrication. The loading conditions were derived based on North Sea wave data pertaining to the offshore field where the FPSO is operating. The stresses were obtained from global FE analysis and fitted Weibull long-term and extreme value distributions. The results of the analyses demonstrate clearly the importance of correcting for crack tip constraint pertaining to both primary and secondary stress and to allow for non-uniform residual stress for shallow surface flaws of known crack heights. However, in combination with fatigue crack growth the effects become less prominent as the failure probability is governed by the uncertainty in the parameters of the crack growth relationship and the long-term stress distribution.

Crack Tip Stress Analysis of the Steam Generator Dissimilar Steel Welded Joint under Residual Stress Field

2019 ◽  
Vol 795 ◽  
pp. 451-457
Author(s):  
Bao Yin Zhu ◽  
Xian Xi Xia ◽  
He Zheng ◽  
Guo Dong Zhang
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Numerical Method ◽  
Steam Generator ◽  
Welded Joint ◽  
Crack Tip ◽  
Residual Stress Field

An typical mode of a structural integrity failure in dissimilar steel welded joints. This paper aims at studying crack tip stress of a steam generator dissimilar welded joint under residual stress field with the method of interaction integral and XFEM. Firstly, the corresponding weak form is obtained where the initial stress field is involved, which is the key step for the XFEM. Then, the interaction integral is applying to calculate the stress intensity factor. In addition, two simple benchmark problems are simulated in order to verify the precision of this numerical method. Finally, this numerical method is applying to calculate the crack tip SIF of the addressed problem. This study finds that the stress intensity factor increases firstly then decreases with the deepening of the crack. The main preponderance of this method concerns avoiding mesh update by take advantage of XFEM when simulating crack propagation, which could avoid double counting. In addition, our obtained results will contribute to the safe assessment of the nuclear power plant steam generator.

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